The authors thank the following staff members and research personnel for their contributions: Matthew Librach, Leila Maghen, Tanya A. Baretto, Shlomit Kenigsberg, and Andr&#233;e Gauthier-Fisher. This work was supported by the The Ontario Research Fund - Research Excellence (ORF-RE, Round #7) and CReATe Program Inc.

All studies involving animals were conducted and reported according to ARRIVE guidelines48. All studies were performed with institutional research ethics board approval (REB number 454-2011, Sunnybrook Research Institute; REB 29889, University of Toronto, Toronto, Canada). All animal procedures were approved by the Animal Care Committee of the University Health Network (Toronto, Canada), and all animals received humane care in compliance with the Guide for the Care and Use of Laboratory Animals, 8th edition (National Institutes of Health 2011).
1. Tissue Culture
<ol>
	<li>Culture FTM HUCPVCs, term HUCPVCs (previously established, n &#8805; 3 independent lines for each)42 and commercially available BMSCs in alpha-minimum essential medium (MEM) supplemented with 10% fetal bovine serum (FBS) and a 1% penicillin/streptomycin (P/S) cocktail. Culture rat primary cardiomyocytes and MSC-cardiomyocyte co-cultures in Dulbecco&#39;s Modified Eagle Medium: Nutrient Mixture F-12 (DMEM-F12) containing 10% FBS and 1% P/S. 
	NOTE: Sterilize the medium using a 0.2-&#181;m filter. Store prepared medium solutions at 4 &#176;C for up to 3 weeks.</li>
	<li>Maintain cell cultures in humidified incubators (95% relative humidity, 37 &#176;C, and 5% CO2) and passage at 70-80% confluency, determined by phase-contrast microscopy. Use appropriate volumes of medium for the size of tissue culture dish used (e.g., 10 mL in a 10-cm dish and 2 mL per well in 6-well tissue culture plate). Use these culture conditions for the duration of the protocol.</li>
	<li>Dissociate MSC monolayers for passaging or MSC-cardiomyocyte co-culture establishment using a dissociation enzyme solution (2 mL/well in a 6-well plate) and incubate at 37 &#176;C for 4 min.</li>
	<li>Transfer the dissociated cells to a 15-mL tube and centrifuge at 400 x g for 5 min.</li>
	<li>Aspirate the supernatant without disrupting the cell pellet and resuspend the cells in 1 mL of a culture medium appropriate for counting using an automated cell counter. Seed the cells as described in the following protocol sections.</li>
</ol>
2. Preparation of Primary Rat Cardiomyocyte-MSC Co-cultures
<ol>
	<li>Obtain heart tissue for primary cardiomyocyte isolation.
	<ol>
		<li>Euthanize rat pups (5-6 days postnatal) using CO2 asphyxiation. Set CO2 chambers to 20% gas replacement (flow rate = 0.2 x chamber volume per min). Confirm exitus by the absence of the pinch reflex.</li>
		<li>Remove the atria with the connecting major blood vessels using sterilized instruments (i.e., forceps and curved scissors)41. Transfer the hearts to 50-mL tubes containing sterile PBS with1% P/S (PBS-P/S) on ice.</li>
		<li>Cut the ventriculi in half and let the blood wash out in a 10-cm dish with 10 mL of PBS-P/S on ice. Cut the ventricular walls into small pieces (diameter = 2-3 mm) using curved scissors.</li>
		<li>Transfer the heart pieces from 10-12 animals to a 50-mL tube using a serological pipette and let them settle.</li>
		<li>Remove as much PBS-P/S as possible without removing any heart pieces. Add 10 mL of new PBS-P/S.</li>
	</ol>
	</li>
	<li>Digest the heart tissue to isolate the cardiomyocytes.
	<ol>
		<li>Allow the heart pieces to settle. Replace the PBS-P/S with 10 mL of 0.15% trypsin in PBS and shake at 37 &#176;C for 10 min.</li>
		<li>Discard the supernatant. Repeat the digestion described in step 2.2.1 three more times, but decant the supernatants into 50-mL collection tubes containing 10 mL of 100% FBS.</li>
	</ol>
	</li>
	<li>Centrifuge the cells (400 x g, 5 min) and aspirate the supernatant. Resuspend the cells in DMEM-F12 containing 10% FBS and 1% P/S and seed onto a 6-well plate (1 x 105 cells/cm2, 2 mL of medium per well).</li>
	<li>After 1 h, transfer the medium containing non-attached cells to a 50-mL tube and discard the attached cells. Count the cells in suspension and re-plate them into new 6-well plates (1 x 105 cells/cm2, 2 mL of DMEM-F12 containing 10% FBS and 1% P/S per well).</li>
	<li>Inhibit cell proliferation with bromodeoxyuridine (BrdU). 
	Caution: BrdU is a strong teratogen and suspected mutagen. Please ensure proper training is provided and refer to the safety data sheet before use.
	<ol>
		<li>Once cells have attached, replace the medium in the 6-well plate with DMEM-F12 containing 10% FBS, 1% P/S (2 mL of medium per well), and 5 &#181;M BrdU. Incubate for 16 h (37 &#176;C, 5% CO2).</li>
		<li>Remove the BrdU-containing medium and replace with DMEM-F12 containing 10% FBS and 1% P/S (2 mL of medium per well).</li>
	</ol>
	</li>
	<li>Prepare pre-stained MSCs.
	<ol>
		<li>Once MSC cultures are at 70-80% confluency in 10-cm dishes, remove the culture medium and add 3 mL of cell dissociation solution. Incubate the dish at 37 &#176;C and 5% CO2 for 5 min.</li>
		<li>Transfer the dissociated cells to a 15-mL tube and centrifuge at 400 x g for 5 min.</li>
		<li>Aspirate the supernatant without disrupting the cell pellet and resuspend the cells in 1 mL of DMEM-F12 containing 10% FBS and 1% P/S for counting using an automated cell counter.</li>
		<li>Dilute the cells to a concentration of 1 x 106 MSC/mL of DMEM-F12 containing 10% FBS and 1% P/S.</li>
		<li>Incubate the MSCs with viable, non-transferable fluorescent dye (5 &#181;M, 30 min, 37 &#176;C, 5% CO2) in 1.5-mL centrifuge tubes for 1 h.</li>
		<li>Centrifuge the tubes at 400 x g for 5 min. Aspirate the supernatant and resuspend the pellet in DMEM-F12 containing 10% FBS and 1% P/S for a cell concentration of 1 x 106 MSC/mL. Repeat this a total of 3 times.</li>
	</ol>
	</li>
	<li>Transfer the MSCs onto cardiomyocytes (step 2.5.2) at a concentration of 10 x 104 cells per well of the 6-well plate.</li>
</ol>
3. Preparation of Aggregate Co-cultures
<ol>
	<li>Prepare a single-cell suspension of MSCs (2 x 104 cells/mL of medium, passage # &#8804; 6) in alpha-MEM supplemented with 10% FBS and 1% P/S (see step 2.6). 
	NOTE: Refer to section 1 of the protocol for the passaging of cells. Alternatively, pre-stain MSCs as per step 2.6.</li>
	<li>Initiate aggregate formation by placing 25-&#181;L drops of cell suspension (500 cells) on the inner surface of the lids of 10-cm tissue culture dishes (up to 50 drops per lid). Place the lids on their bottom counterparts containing PBS-P/S. Incubate at 37 &#176;C and 5% CO2. 
	NOTE: Place 5-7 mL of PBS-P/S into the culture dish below the hanging drops to avoid drop evaporation.</li>
	<li>Observe aggregate formation in the drops after 3 days using a stereomicroscope. If over 40 out of 50 drops contain formed aggregates, collect the drops from the lids using a 1-mL micropipette and transfer the aggregates directly onto primary rat cardiomyocyte monolayers (prepared in steps 2.1-2.7; 10 drops/well). Avoid vigorous pipetting to preserve aggregate integrity.</li>
	<li>Keep aggregate co-cultures in the incubators for up to 2 weeks, changing the full volume of medium (2 mL of DMEM-F12 containing 10% FBS and 1% P/S per well) every 72 h.
	<ol>
		<li>Daily observe aggregates attaching on feeder cell layers using bright-field microscopy. Record contracting aggregates when observed.</li>
	</ol>
	</li>
	<li>Prepare aggregates for analysis.
	<ol>
		<li>Remove the medium and add 2 mL of PBS per well of a 6-well tissue culture dish. Remove the PBS and add 2 mL of dissociation solution per well. Incubate for 3 min at 37 &#176;C and 5% CO2.</li>
		<li>Centrifuge at 400 x g for 5 min to obtain a cell pellet. Resuspend in medium, as specified for the applications described in the subsequent steps (see steps 4.1, 5.1, and 6.1) and pass through a 70-&#181;m cell strainer.</li>
	</ol>
	</li>
</ol>
4. Flow Cytometry (FC) and Fluorescence-activated Cell Sorting (FACS)
<ol>
	<li>Incubate cell suspensions (1 x 105 cells in 200 &#181;L of PBS containing 3% FBS) with fluorophore-conjugated (FITC or APC) primary antibodies (i.e., CD49f, Cx43, TRA-1-85, HLA-A, HLA-G, and SIRPA for FC or TRA-1-85 for FACS; 1:40) at 4 &#176;C for 30 min, protected from light.</li>
	<li>Centrifuge (400 x g, 5 min) and resuspend the cells in 1 mL of PBS with 3% FBS for FC or PBS with 0.5% FBS for FACS. 
	NOTE: The FC of MSCs was optimized by Hong et al.41.</li>
	<li>Maintain the cells at 4 &#176;C in the dark until they are ready to be analyzed by FC (at least 1 x 104 events) or FACS. Sort the cells as described41. Re-plate TRA-1-85 high-positive sorted cells in 6-well plates (1 x 104 cells/well, 2 mL of DMEM-F12 containing 10% FBS and 1% P/S) within 1 h. 
	NOTE: For the gating strategy of the TRA-1-85 human cell surface antigen, see the Supplementary Figure.</li>
</ol>
5. Immunocytochemistry (ICC) and Microscopy
<ol>
	<li>Re-plate the cell suspensions obtained from the co-cultures (step 3.5.2) or FACS (section 4) onto chamber slides (1 x 104 cells/well, 2 mL of DMEM-F12 containing 10% FBS and 1% P/S per well). Let the cells attach overnight in a tissue culture incubator (see section 1 for the conditions).</li>
	<li>Fix the cells using 3 mL of 4% paraformaldehyde (PFA) in PBS for 15 min at room temperature. Wash 3 times with 3 mL of PBS containing 1% bovine serum albumin (BSA; PBS-BSA) for 5 min per wash. 
	Caution: Wear appropriate personal protective equipment when handling PFA.</li>
	<li>Permeabilize the cells in 3 mL of PBS-BSA with 0.1% Triton X-100. Incubate at room temperature for 10 min for intracellular antigens (i.e., alpha sarcomeric actinin (aSarc) and Cx43), or 25 min for intra-nuclear antigens (i.e., Mef2c and human nuclear antigen (HuNu)). Wash 3 times with 3 mL of PBS-BSA for 5 min per wash.</li>
	<li>Block the samples against non-specific antibody reactions with 3 mL of PBS containing 5% normal goat serum (NGS) and 1% BSA for 15 min at room temperature. Wash 3 times with 3 mL of PBS-BSA for 5 min per wash.</li>
	<li>Incubate the cells in the primary antibodies (i.e., Mef2c, aSarc, Cx43, and HuNu) diluted 1:200 in 3 mL of PBS-BSA at 4 &#176;C overnight.</li>
	<li>Wash 3 times with 3 mL of PBS-BSA for 5 min per wash and incubate with secondary antibodies for 30 min at room temperature. Wash 3 times with 3 mL of PBS-BSA for 5 min per wash.</li>
	<li>Store the stained specimens in 3 mL of of mounting medium.</li>
	<li>Acquire images using a fluorescence microscope. Use a 10X objective (NA = 0.3), and a 20X objective (NA = 0.45) for lower-magnification imaging. Use fluorescence filter cubes and wavelengths for GFP (ex = 470/22 nm, em = 525/50 nm) and RFP (ex = 531/40 nm, em = 593/40 nm) for the secondary antibodies used (see the Materials and Equipment Table).</li>
	<li>Quantify images using imaging software (see the Materials and Equipment Table for the recommended software). Normalize the fluorescence intensity readings to the secondary control acquisitions.</li>
</ol>
6. RNA Isolation and Quantitative RT-PCR
<ol>
	<li>Prepare RNA samples from undifferentiated MSC cultures or MSCs sorted from co-cultures using column-based RNA isolation, according to the manufacturer&#39;s instructions. Prepare 1 x 104 to 1 x 106 cells in 0.7 mL of cell lysis buffer (provided with the RNA isolation kit) per sample.</li>
	<li>Prepare cDNA from up to 2 &#181;g of RNA per 100-&#181;L RT reaction.</li>
	<li>Perform qPCR using 10 ng of cDNA per reaction (40 cycles, 60 &#176;C annealing/extending temperature).
	<ol>
		<li>Use primers for human MY6H and cTnT in a 500-nM concentration and 1-100 ng of cDNA per reaction (see the Materials and Equipment Table). Use GAPDH, ACTB, and HPRT as internal housekeeping normalizers. Use commercially available human-induced pluripotent stem cell-derived cardiomyocytes as a positive control. 
		NOTE: Express the fold-change of expression compared to undifferentiated MSC-derived cDNA samples.</li>
	</ol>
	</li>
</ol>

Dr. Clifford L. Librach is joint holder of the patent: Methods of isolation and use of cells derived from first trimester umbilical cord tissue, granted in Canada and Australia.

The cardiac differentiation of stem cells has been under development for over 2 decades, with several different strategies being used to generate cardiomyocyte-like cells from MSC sources. Many of these strategies, however, are inefficient, and the conditions used are often not representative of the environment transplanted cells encounter in vivo.
In contrast to existing methods, the protocol presented here utilizes a combination of primary cardiac feeder layers and MSC aggregate formation. The primary cardiac feeder layers provide a differentiation environment similar to that which the hMSCs are exposed to upon transplantation. The aggregates generate an environment with oxygen and nutrient gradients, which can have an inductive effect on initiating lineage commitment. PSC- and ESC-based cardiac differentiation strategies using hypoxic preconditioning and aggregate formation have established this inductive effect on stem cells5,52,53. Additionally, a 3D structure better resembles the cell-to-cell connections provided in vivo. Using this method, we successfully produced synchronously contracting hMSC aggregates-the first time an hMSC type was able to achieve this, to our knowledge. Importantly, only the youngest hMSC cell source applied, FTM HUCPVCs, exhibited this ability.
A significant advantage of using either na&#239;ve or pre-differentiated MSCs over ESCs or PSCs for cardiac regeneration lies in their immunomodulatory or immunoprivileged properties. However, even in the case of MSCs, immunomodulatory properties vary with their age and source54. BMSCs have been shown to change their immunogenic properties post-differentiation, which often leads to their rejection upon implantation55. As previously described, MSCs from the umbilical cord origin possess special immune privilege56 due to their in utero origin. Using the protocol described above, even after differentiation into cardiomyocyte-like cells, term and FTM HUCPVCs exhibited high levels of HLA-G (that actively attenuates the innate immune response) and maintained low levels of HLA-A (that determines T-cell mediated cytotoxicity).
This differentiation protocol has the advantage of conveniently allowing for multiple levels of analysis. First, the live imaging of functional, contracting aggregates is more feasible than distinguishing single cells integrated into a feeder layer. As the protocol utilizes mixed-species co-cultures, human-specific primers are applied to qPCR analysis, while FACS and ICC provide the rapid identification of phenotype- specifically, cardiac marker expression (Figure 2). Using the protocol as described, elevated levels of SIRPA, cTnT, MYH6, aSarc, Mef2c, and Cx43 were detected. In conjunction with HuNu, it is possible to identify the expression of Mef2c and aSarc in differentiated hMSCs and to distinguish from the rat cardiomyocyte-derived feeder layers or fused cells. While the identification of contracting aggregates on the feeder layer is relatively easy, collecting or harvesting them can pose a limitation. Microscopes equipped with a micromanipulator can be employed to handle this challenge. Alternatively, human cells can be efficiently sorted from co-cultures using human-specific anti-TRA-1-85 antibodies. While the co-cultures also present the challenge of potential cell fusion, this too can be overcome using a combination of nuclear and cell-surface human marker tracers (Supplementary Figure 1).
A possible modification of our differentiation method is to adjust the formation of aggregates. Our results suggest that aggregate size can be a critical parameter for optimal differentiation. Assuming that aggregation is selective for more adhesive cells, it can act as a pre-selection step for CD49f-positive hMSCs. Enhanced MSC sphere formation has been linked to increased CD49f expression49, and CD49f is also associated with higher stemness because it is directly connected to SOX2 and OCT449. We observed lower numbers of CD49f-positive cells in older sources of hMSCs compared to FTM HUCPVCs, which could explain the diminished aggregate size observed. We theorize that this selection can be compensated for by increasing the number of hMSCs per aggregate to achieve a higher aggregate size, thus possibly increasing the efficiency of aggregation-induced differentiation.
Future applications might require modifications to the protocol as well. It is imperative that clinical applications of pre-differentiated hMSCs take place in xeno-free conditions. The contracting aggregates produced using this protocol could also be used for the creation of engineered heart muscle tissues. To produce a clinically applicable product, a cGMP-compliant workflow is necessary. While xeno-free culture medium is available for hMSCs, providing an animal-free feeder layer might be challenging. However, applying pre-differentiated feeder layers of other stem cell sources, such as iPSCs, is a possible solution.
In conclusion, the differentiation method described can be applied to produce functional cardiomyocyte-like cells from young sources of hMSCs in a convenient and reproducible manner.

Congestive heart failure (CHF) persists as a leading cause of morbidity and mortality worldwide. CHF often occurs following the massive loss of cardiomyocytes and the development of cell-free scar tissue as the pathological result of a myocardial infarction (MI)1. While the heart is a partially self-renewing organ, the resident stem and progenitor cell pool responsible for executing tissue regeneration significantly diminishes in abundance and function in aged patients, often becoming insufficient for optimal recovery after injury. Thus, there is great interest in developing experimental treatments that involve the transplantation of healthy donor cells into the damaged myocardium. It is imperative that the donor cells not only restore the structure of the tissue, but also achieve the functional recovery of the affected myocardium.
The native heart employs heart tissue-resident and endogenous bone marrow-originated stem cells for post-injury repair2,3,4. Regenerative cells- host- and donor-derived alike- must have the capacity to obtain the appropriate phenotype and function in the microenvironment of the remodeling myocardium, along with the ability to efficiently and safely replace the lost cells. In vitro differentiation methods have been used extensively to achieve high-efficiency, stem cell-based cardiomyocyte production5,6. The expression profile of cardiac lineage markers is used to define the process of stem cell differentiation towards the cardiac lineage7. Early differentiation markers, such as NKX2.5, myocyte enhancer factor 2C (Mef2c), and GATA48,9, can be an indication of the initiation of the cardiomyogenic process. Mature cardiomyocyte markers commonly used to assess differentiation efficacy are signal regulatory protein &#945; (SIRPA)10, cardiac troponin T (cTnT)11, heavy chain cardiac myosin (MYH6)8,12,13, and connexin 43 (Cx43)14,15,16. The methods using embryonic stem cells (ESCs) and pluripotent stem cells (PSCs) have been thoroughly optimized and discussed regarding the details of inductive factors, oxygen and nutrient gradients, and the exact timing of action5,6,7,17,18. Nonetheless, ESC- and PSC-based technologies still present multiple ethical and safety concerns, along with suboptimal electrophysiological and immunological features19,20. Hosts transplanted with these cells often experience immunorejection and require permanent immunosuppression. This is mainly due to mismatching major histocompatibility complex (MHC) molecules in the host and donor and to the resulting T-cell response21. While individual MHC class I matching is a possible solution, a more accessible clinical practice would require a cell source that is universally immunoprivileged to overcome the concern of rejection.
As an alternative cell source for use in clinical applications, MSCs and in particular, BMSCs, have been investigated for use in tissue regeneration since their initial description in 199522. MSCs are believed to be resident regenerative cells that can be found in nearly any vascularized tissue23. Upon isolation from the desired source, MSCs can easily be expanded in culture, have extensive paracrine capacity, and often possess immunoprivileged or immunomodulatory properties24,25. Their safety and efficacy have already been shown in several pre-clinical studies, in particular for cardiac regeneration3,26.
Many MSC differentiation strategies utilize pharmacological agents, such as 5-azacytidine22 and DMSO27, and growth or morphogenic factors, like BMPs5,7,28,29 or angiotensin-II30, with variable efficiency. These strategies, however, are not based on the obstacles that a na&#239;ve regenerative cell is likely to encounter after homing or being delivered to the site of injury in vivo. More physiologically relevant strategies, while more difficult to define and manipulate, are based on the premise that MSC differentiation can be induced through signals from the tissue microenvironment itself. Previous studies have shown that exposure to the cardiac cell lysates31 or ventricular myocardium32,33, or direct contact with primary cardiomyocytes in vitro15,34, can increase the expression of cardiac markers in MSCs. Others have demonstrated spontaneous cardiomyogenesis after treating cardiac injuries with MSCs35,36,37,38, although in part, the fusion of BMSCs and cardiomyocytes39,40 generated the nascent myocardium. To our knowledge, functional, spontaneously contracting cardiomyocytes from human MSCs (hMSCs) of any tissue source have not yet been reported.
The current consensus is that all MSCs arise from perivascular cells23. Young MSCs with pericyte properties can be isolated from the perivascular region of human umbilical cord tissue41,42,43. In comparison to BMSCs, HUCPVCs possess increased differentiation potential and several other regenerative advantages, both in vitro41,44 and in vivo45,46,47. Notably, the source being the maternal-fetal interface, HUCPVCs have significantly lower immunogenicity compared to adult sources of MSCs. Our research focuses on the characterization and pre-clinical applications of FTM HUCPVCs, the youngest source of MSCs investigated, which we have previously shown to have increased proliferative and higher multilineage differentiation capacities, including in the cardiomyogenic lineage41.
Here, we present a protocol that combines aggregate formation and primary cardiac cell feeder layers as inductive forces to attain the complete cardiomyogenic differentiation of MSCs. Aggregates provide a 3D environment, which better models conditions in vivo compared to 2D adherent cultures. Utilizing cardiac feeder layers provides an environment that is representative of the ultimate transplantation site for the MSCs. We demonstrate that younger sources of MSCs isolated from pre- or post-natal umbilical cords have a higher capacity to form aggregates and to reach the cardiac phenotype compared to adult BMSCs, while still maintaining their immune-privilege. Besides the steep elevation of cardiac lineage marker genes and the induced expression of intracellular (i.e., cTnT and MYH6) and cell-surface proteins (i.e., SIRPA and Cx43) specific for cardiomyocytes, we show that the differentiation potential of FTM HUCPVCs can be harnessed with this method and that they can give rise to spontaneously contracting cardiomyocyte-like cells.

<table><tbody><tr><td>0.25% Trypsin/EDTA</td><td>Gibco</td><td>25200056</td><td>For cell dissociation</td></tr><tr><td>Alpha-MEM</td><td>Gibco</td><td>12571071</td><td>For HUCPVC and BMSC culture media.</td></tr><tr><td>PE-conjugated anti-human/mouse CD49f antibody</td><td>Biolegend</td><td>313612</td><td>Integrin marker for FC</td></tr><tr><td>APC-conjugated human Cx43/GJA1 antibody</td><td>R&amp;amp;D Systems</td><td>FAB7737A</td><td>Connexin 43 marker for FC</td></tr><tr><td>FITC-conjugated HLA-A2 antibody</td><td>Genway Biotech Inc.</td><td>GWB-66FBD2</td><td>Immunogenicity marker for FC</td></tr><tr><td>FITC-conjugated anti-HLA-G [MEM-G/9] antibody</td><td>Abcam</td><td>ab7904</td><td>Immunogenicity marker for FC</td></tr><tr><td>FITC-conjugated mouse anti-human SIRPA/CD172a antibody</td><td>AbD Serotec/Bio-Rad</td><td>MCA2518F</td><td>Cardiac marker for FC</td></tr><tr><td>APC-conjugated human TRA-1-85/CD147 antibody</td><td>R&amp;amp;D Systems</td><td>FAB3195A</td><td>Human cell marker for FC and FACS</td></tr><tr><td>FITC-conjugated human TRA-1-85/CD147 antibody</td><td>R&amp;amp;D Systems</td><td>FAB3195F</td><td>Human cell marker for FC and FACS</td></tr><tr><td>Anti-connexin 43/GJA1 antibody</td><td>Abcam</td><td>ab11370</td><td>Cx43. For ICC</td></tr><tr><td>Goat anti-rabbit IgG (H+L) cross-absorbed secondary antibody, Alexa Fluor 555</td><td>Life Technologies</td><td>A-21428</td><td>For ICC</td></tr><tr><td>Anti-sarcomeric alpha actinin [EA-53] antibody</td><td>Abcam</td><td>ab9465</td><td>aSARC. For ICC</td></tr><tr><td>Goat anti-mouse IgM heavy chain cross-absorbed secondary antibody, Alexa Fluor 555</td><td>Life Technologies</td><td>A-21426</td><td>For ICC</td></tr><tr><td>Mef2C (D80C1) XP rabbit antibody</td><td>New England BioLabs Ltd.</td><td>5030S</td><td>For ICC</td></tr><tr><td>Donkey anti-rabbit IgG (H+L) secondary antibody, Alexa Fluor 488</td><td>Life Technologies</td><td>A-21206</td><td>For ICC</td></tr><tr><td>Anti-nuclei (HuNu) (clone 235-1) antibody</td><td>EMD Millipore</td><td>MAB1281</td><td>For ICC</td></tr><tr><td>MZ9.5 Stereomicroscope</td><td>Leica</td><td></td><td>For imaging aggregates.</td></tr><tr><td>1.5 ml centrifuge microtubes</td><td>Axygen</td><td>MCT-150-C</td><td>For staining MSCs with fluorescent dye.</td></tr><tr><td>ImageJ</td><td></td><td></td><td>Open source image processing software.</td></tr><tr><td>Aria II&amp;nbsp;</td><td>BD</td><td></td><td>UHN SickKids FC Facility. For cell sorting.</td></tr><tr><td>Bone marrow mesechymal stromal cells</td><td>Lonza</td><td>PT-2501</td><td>BMSCs</td></tr><tr><td>Bovine serum albumin</td><td>Sigma-Aldrich</td><td>A7030-100G</td><td>BSA. To prepare solutions for ICC</td></tr><tr><td>BrdU</td><td>EMD Millipore</td><td>MAB3424</td><td>Caution: BrdU is a strong teratogen and suspected mutagen. Please ensure proper training and refer to the SDS before use.</td></tr><tr><td>Canto II</td><td>BD</td><td></td><td>UHN SickKids FC Facility. For flow cytometry.</td></tr><tr><td>cDNA EcoDry Premix</td><td>Clontech/Takara</td><td>639570</td><td>For preparation of cDNA for qPCR</td></tr><tr><td>CellTracker Green CMFDA Dye</td><td>Life Technologies</td><td>C7025</td><td>Fluorescent imaging of cell cytoplasm</td></tr><tr><td>Countess automated cell counter</td><td>Invitrogen Inc.</td><td>C10227</td><td>For cell counting</td></tr><tr><td>DMEM-F12</td><td>Sigma-Aldrich</td><td>D6421</td><td>For rat primary cardiomyocyte culture medium.</td></tr><tr><td>Dulbecco&#039;s Phosphate Buffered Saline</td><td>Gibco</td><td>10010023</td><td>D-PBS, without Ca&lt;sup&gt;2+&lt;/sup&gt;, Mg&lt;sup&gt;2+&lt;/sup&gt;</td></tr><tr><td>EVOS</td><td>Life Technologies</td><td></td><td>In-house fluorescent microscope</td></tr><tr><td>FACSCalibur</td><td>BD</td><td></td><td>In-house. For flow cytometry.</td></tr><tr><td>Fetal bovine serum (Hyclone)</td><td>GE Healthcare</td><td>SH3039603</td><td>FBS. Component of cell culture medium.</td></tr><tr><td>IDT Prime Time qPCR probes</td><td>Integrated Data Technologies</td><td>FAM fluorophore</td><td>http://www.idtdna.com/pages/products/gene-expression/primetime-qpcr-assays-and-primers</td></tr><tr><td>Lab Vision PermaFluor Aqueous Mounting Medium</td><td>ThermoScientific</td><td>TA-030-FM</td><td>For storage of cells to undergo ICC</td></tr><tr><td>LSR II&amp;nbsp;</td><td>BD</td><td></td><td>UHN SickKids FC Facility. For flow cytometry.</td></tr><tr><td>MoFlo Astrios</td><td>Beckman Coulter</td><td></td><td>UHN SickKids FC Facility. For cell sorting.</td></tr><tr><td>Normal goat serum</td><td>Cell Signaling Technology</td><td>5425S</td><td>NGS. Used in blocking solution for ICC</td></tr><tr><td>Nunc Lab-Tek II Chamber Coverglass, 8-wells</td><td>Thermo Scientific Nunc</td><td>155409</td><td>To prepare samples for ICC</td></tr><tr><td>OmniPur Triton X-100 Surfactant</td><td>EMD Millipore</td><td>9410-OP</td><td>As a component of permeabilizing solution when preparing cells for ICC</td></tr><tr><td>Paraformaldehyde, 16% Solution, EM Grade</td><td>Electron Microscopy Sciences</td><td>15710</td><td>For fixing cells for ICC.</td></tr><tr><td>Penicillin/streptomycin</td><td>Gibco</td><td>15140122</td><td>Component of cell culture medium.</td></tr><tr><td>Primers</td><td>Sigma</td><td>Custom Standard DNA Oligos, Desalted, 0.2 &amp;mu;mol</td><td>&lt;strong&gt;CTnT_F:&lt;/strong&gt; GGC AGC GGA AGA GGA TGC TGA A; &lt;strong&gt;CTnT_R:&lt;/strong&gt; GAG GCA CCA AGT TGG GCA TGA ACG A; &lt;strong&gt;MYH6 F:&lt;/strong&gt; GCA AAG TAC TGG ATG ACA CGC T; &lt;strong&gt;MYH6 R:&lt;/strong&gt; GTC ATT GCT GAA ACC GAG AAT G</td></tr><tr><td>Quorum Spinning Disk Confocal</td><td>Zeiss</td><td></td><td>SickKids Imaging Facility</td></tr><tr><td>ReproCardio hiPS cell derived cardiomyocytes</td><td>ReproCell</td><td>RCD001N</td><td>Positive control for qPCR</td></tr><tr><td>RNeasy mini kit</td><td>Qiagen</td><td>74106</td><td>To isolate RNA for qPCR</td></tr><tr><td>Rotor-Gene SYBR Green PCR Kit</td><td>Qiagen</td><td>204074</td><td>For qPCR with master mix</td></tr><tr><td>RPMI 1640</td><td>Gibco</td><td>A1049101</td><td>For MSC, monocyte coculture medium.</td></tr><tr><td>TaqMan qPCR primer assays</td><td>Thermo Fisher Scientific</td><td>4444556</td><td>For qPCR</td></tr><tr><td>Trypan Blue</td><td>Life Technologies</td><td>T10282</td><td>Staining of cells for viability and counting</td></tr><tr><td>Trypsin</td><td>Gibco</td><td>272500108</td><td>For cell dissociation</td></tr><tr><td>Volocity</td><td>Perkin-Elmer</td><td>Volocity 6.3</td><td>Imaging software</td></tr><tr><td>0.2 &amp;mu;m pore filter</td><td>Thermo Fisher Scientific</td><td>566-0020</td><td>For sterilizing tissue culture media</td></tr><tr><td>HERAcell 150i CO&lt;sub&gt;2&lt;/sub&gt; Incubator</td><td>Thermo Fisher Scientific</td><td>51026410</td><td>For incubating cells</td></tr><tr><td>Dulbecco&#039;s phosphate buffered saline</td><td>Sigma-Aldrich</td><td>D8537</td><td>PBS. 1X, Without calcium chloride and magnesium chloride</td></tr><tr><td>Forceps</td><td>Almedic</td><td>7727-A10-704</td><td>For handing rat heart. Can use any similar forceps.</td></tr><tr><td>Scissors</td><td>Fine Science Tools</td><td>14059-11</td><td>For mincing rat heart. Curved scissors recommended.</td></tr><tr><td>50 mL tube</td><td>BD Falcon</td><td>352070</td><td>For collection during cardiomyocyte collection and general tissue culture procedures</td></tr><tr><td>15 mL tube</td><td>BD Falcon</td><td>352096</td><td>For general tissue culture procedures</td></tr><tr><td>6-well plates</td><td>Thermo Scientific Nunc</td><td>CA73520-906</td><td>For tissue culture</td></tr><tr><td>10 cm tissue culture dishes</td><td>Corning</td><td>25382-428</td><td>For aggregate formation</td></tr><tr><td>Axiovert 40C Microscope</td><td>Zeiss</td><td></td><td>For bright-field imaging through out tissue culture and the rest of the protocol</td></tr><tr><td>70 &amp;mu;m cell strainer</td><td>Fisherbrand</td><td>22363548</td><td>To ensure a single cell suspension before flow cytometry or sorting</td></tr><tr><td>Triton X-100</td><td>EMD Millipore</td><td>9410-1L</td><td>Used in permeabilization solution for ICC</td></tr><tr><td>Hoechst 33342</td><td>Thermo Fisher Scientific</td><td>H1399</td><td>Stain used during visualization of Cx43 localization</td></tr></tbody></table>

in vitro differentiation of human mesenchymal stem cells into functional cardiomyocyte-like cells

Myocardial infarction and the subsequent ischemic cascade result in the extensive loss of cardiomyocytes, leading to congestive heart failure, the leading cause of mortality worldwide. Mesenchymal stem cells (MSCs) are a promising option for cell-based therapies to replace current, invasive techniques. MSCs can differentiate into mesenchymal lineages, including cardiac cell types, but complete differentiation into functional cells has not yet been achieved. Previous methods of differentiation were based on pharmacological agents or growth factors. However, more physiologically relevant strategies can also enable MSCs to undergo cardiomyogenic transformation. Here, we present a differentiation method using MSC aggregates on cardiomyocyte feeder layers to produce cardiomyocyte-like contracting cells.
Human umbilical cord perivascular cells (HUCPVCs) have been shown to have a greater differentiation potential than commonly investigated MSC types, such as bone marrow MSCs (BMSCs). As an ontogenetically younger source, we investigated the cardiomyogenic potential of first-trimester (FTM) HUCPVCs compared to older sources. FTM HUCPVCs are a novel, rich source of MSCs that retain their in utero immunoprivileged properties when cultured in vitro. Using this differentiation protocol, FTM and term HUCPVCs achieved significantly increased cardiomyogenic differentiation compared to BMSCs, as indicated by the increased expression of cardiomyocyte markers (i.e., myocyte enhancer factor 2C, cardiac troponin T, heavy chain cardiac myosin, signal regulatory protein &#945;, and connexin 43). They also maintained significantly lower immunogenicity, as demonstrated by their lower HLA-A expression and higher HLA-G expression. Applying aggregate-based differentiation, FTM HUCPVCs showed increased aggregate formation potential and generated contracting cells clusters within 1 week of co-culture on cardiac feeder layers, becoming the first MSC type to do so. 
Our results demonstrate that this differentiation strategy can effectively harness the cardiomyogenic potential of young MSCs, such as FTM HUCPVCs, and suggests that in vitro pre-differentiation could be a potential strategy to increase their regenerative efficacy in vivo.

Watch this Scientific Journal Video about In Vitro Differentiation of Human Mesenchymal Stem Cells into Functional Cardiomyocyte-like Cells at JoVE.com

In Vitro Differentiation of Human Mesenchymal Stem Cells into Functional Cardiomyocyte-like Cells

Here, we present a method to efficiently harness the cardiac differentiation potential of young sources of human mesenchymal stem cells in order to generate functional, contracting, cardiomyocyte-like cells in vitro.

In Vitro Differentiation of Human Mesenchymal Stem Cells into Functional Cardiomyocyte-like Cells

Myocardial infarction and the subsequent ischemic cascade result in the extensive loss of cardiomyocytes, leading to congestive heart failure, the leading ...

in-vitro-differentiation-human-mesenchymal-stem-cells-into-functional

Nanyang Technological University

Research

JoVE Journal

Developmental Biology

10.9K Views.  Create Fertility Centre. Hier presenteren we een methode voor het efficiënt benutten van het potentieel van de cardiale differentiatie van jonge bronnen van menselijke mesenchymale stamcellen om te genereren van functionele, aanbestedende, cardiomyocyte-achtige cellen in vitro.

Video: In Vitro Differentiation of Human Mesenchymal Stem Cells into Functional Cardiomyocyte-like Cells

Derivation of Cardiac Progenitor Cells from Embryonic Stem Cells

Cardiac progenitor cells (CPCs) have the capacity to differentiate into cardiomyocytes, smooth muscle cells (SMC), and endothelial cells and hold great promise in cell therapy against heart disease. Among various methods to isolate CPCs, differentiation of embryonic stem cell (ESC) into CPCs attracts great attention in the field since ESCs can provide unlimited cell source. As a result, numerous strategies have been developed to derive CPCs from ESCs. In this protocol, differentiation and purification of embryonic CPCs from both mouse and human ESCs is described. Due to the difficulty of using cell surface markers to isolate embryonic CPCs, ESCs are engineered with fluorescent reporters activated by CPC-specific cre recombinase expression. Thus, CPCs can be enriched by fluorescence-activated cell sorting (FACS). This protocol illustrates procedures to form embryoid bodies (EBs) from ESCs for CPC specification and enrichment. The isolated CPCs can be subsequently cultured for cardiac lineage differentiation and other biological assays. This protocol is optimized for robust and efficient derivation of CPCs from both mouse and human ESCs.

In this protocol, derivation of cardiac progenitor cells from both mouse and human embryonic stem cells will be illustrated. A major strategy in this protocol is to enrich cardiac progenitor cells with flow cytometry using fluorescent reporters engineered into the embryonic stem cell lines.

Cardiac progenitor cells (CPCs) have the capacity to differentiate into cardiomyocytes, smooth muscle cells (SMC), and endothelial cells and hold great ...

Derivation of Highly Purified Cardiomyocytes from Human Induced Pluripotent Stem Cells Using Small Molecule-modulated Differentiation and Subsequent Glucose Starvation

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have become an important cell source to address the lack of primary cardiomyocytes available for basic research and translational applications. To differentiate hiPSCs into cardiomyocytes, various protocols including embryoid body (EB)-based differentiation and growth factor induction have been developed. However, these protocols are inefficient and highly variable in their ability to generate purified cardiomyocytes. Recently, a small molecule-based protocol utilizing modulation of Wnt/&#946;-Catenin signaling was shown to promote cardiac differentiation with high efficiency. With this protocol, greater than 50%-60% of differentiated cells were cardiac troponin-positive cardiomyocytes were consistently observed. To further increase cardiomyocyte purity, the differentiated cells were subjected to glucose starvation to specifically eliminate non-cardiomyocytes based on the metabolic differences between cardiomyocytes and non-cardiomyocytes. Using this selection strategy, we consistently obtained a greater than 30% increase in the ratio of cardiomyocytes to non-cardiomyocytes in a population of differentiated cells. These highly purified cardiomyocytes should enhance the reliability of results from human iPSC-based in vitro disease modeling studies and drug screening assays.

Here, we describe a robust protocol for human cardiomyocyte derivation that combines small molecule-modulated cardiac differentiation and glucose deprivation-mediated cardiomyocyte purification, enabling production of purified cardiomyocytes for the purposes of cardiovascular disease modeling and drug screening.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have become an important cell source to address the lack of primary cardiomyocytes ...

Differentiation of Atrial Cardiomyocytes from Pluripotent Stem Cells Using the BMP Antagonist Grem2

Protocols for generating populations of cardiomyocytes from pluripotent stem cells have been developed, but these generally yield cells of mixed phenotypes. Researchers interested in pursuing studies involving specific myocyte subtypes require a more directed differentiation approach. By treating mouse embryonic stem (ES) cells with Grem2, a secreted BMP antagonist that is necessary for atrial chamber formation in vivo, a large number of cardiac cells with an atrial phenotype can be generated. Use of the engineered Myh6-DSRed-Nuc pluripotent stem cell line allows for identification, selection, and purification of cardiomyocytes. In this protocol embryoid bodies are generated from Myh6-DSRed-Nuc cells using the hanging drop method and kept in suspension until differentiation day 4 (d4). At d4 cells are treated with Grem2 and plated onto gelatin coated plates. Between d8-d10 large contracting areas are observed in the cultures and continue to expand and mature through d14. Molecular, histological and electrophysiogical analyses indicate cells in Grem2-treated cells acquire atrial-like characteristics providing an in vitro model to study the biology of atrial cardiomyocytes and their response to various pharmacological agents.

Generating cardiomyocytes from pluripotent stem cells in vitro allows access to large amounts of cardiac tissue in vitro for basic science and clinical applications. This protocol uses the atrializing factor Grem2 to both increase the numbers of cardiomyocytes obtained and to generate cardiomyocytes with an atrial phenotype.

Protocols for generating populations of cardiomyocytes from pluripotent stem cells have been developed, but these generally yield cells of mixed ...

In vitro Differentiation of Mouse Embryonic Stem (mES) Cells Using the Hanging Drop Method

Stem cells have the remarkable potential to develop into many different cell types. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, This promising of science is leading scientists to investigate the possibility of cell-based therapies to treat disease.

When culture in suspension without antidifferentiation factors, embryonic stem cells spontaneously differentiate and form three-dimensional multicellular aggregates. These cell aggregates are called embryoid bodies(EB). Hanging drop culture is a widely used EB formation induction method. The rounded bottom of hanging drop allows the aggregation of ES cells which can provide mES cells a good environment for forming EBs. The number of ES cells aggregatied in a hanging drop can be controlled by varying the number of cells in the initial cell suspension to be hung as a drop from the lid of Petri dish. Using this method we can reproducibly form homogeneous EBs from a predetermined number of ES cells. 

In vitro Differentiation of Mouse Embryonic Stem mES Cells Using the Hanging Drop Method

This video demonstrates how to conduct in vitro differentiation of mouse embryonic stem cells to embryoid bodies using the hanging drop method.

Stem cells have the remarkable potential to develop into many different cell types. When a stem cell divides, each new cell has the potential to either ...

Biology

Electrophysiological Analysis of human Pluripotent Stem Cell-derived Cardiomyocytes (hPSC-CMs) Using Multi-electrode Arrays (MEAs)

Cardiomyocytes can now be derived with high efficiency from both human embryonic and human induced-Pluripotent Stem Cells (hPSC). hPSC-derived cardiomyocytes (hPSC-CMs) are increasingly recognized as having great value for modeling cardiovascular diseases in humans, especially arrhythmia syndromes. They have also demonstrated relevance as in vitro systems for predicting drug responses, which makes them potentially useful for drug-screening and discovery, safety pharmacology and perhaps eventually for personalized medicine. This would be facilitated by deriving hPSC-CMs from patients or susceptible individuals as hiPSCs. For all applications, however, precise measurement and analysis of hPSC-CM electrical properties are essential for identifying changes due to cardiac ion channel mutations and/or drugs that target ion channels and can cause sudden cardiac death. Compared with manual patch-clamp, multi-electrode array (MEA) devices offer the advantage of allowing medium- to high-throughput recordings. This protocol describes how to dissociate 2D cell cultures of hPSC-CMs to small aggregates and single cells and plate them on MEAs to record their spontaneous electrical activity as field potential. Methods for analyzing the recorded data to extract specific parameters, such as the QT and the RR intervals, are also described here. Changes in these parameters would be expected in hPSC-CMs carrying mutations responsible for cardiac arrhythmias and following addition of specific drugs, allowing detection of those that carry a cardiotoxic risk.

Electrophysiological Analysis of human Pluripotent Stem Cell-derived Cardiomyocytes hPSC-CMs Using Multi-electrode Arrays MEAs

Electrophysiological characterization of cardiomyocytes derived from human Pluripotent Stem Cells (hPSC-CMs) is crucial for cardiac disease modeling and for determining drug responses. This protocol provides the necessary information to dissociate and plate hPSC-CMs on multi-electrode arrays, measure their field potential, and a method for analyzing QT and RR intervals.

Cardiomyocytes can now be derived with high efficiency from both human embryonic and human induced-Pluripotent Stem Cells (hPSC). hPSC-derived ...

Construction of Defined Human Engineered Cardiac Tissues to Study Mechanisms of Cardiac Cell Therapy

Human cardiac tissue engineering can fundamentally impact therapeutic discovery through the development of new species-specific screening systems that replicate the biofidelity of three-dimensional native human myocardium, while also enabling a controlled level of biological complexity, and allowing non-destructive longitudinal monitoring of tissue contractile function. Initially, human engineered cardiac tissues (hECT) were created using the entire cell population obtained from directed differentiation of human pluripotent stem cells, which typically yielded less than 50% cardiomyocytes. However, to create reliable predictive models of human myocardium, and to elucidate mechanisms of heterocellular interaction, it is essential to accurately control the biological composition in engineered tissues. 
To address this limitation, we utilize live cell sorting for the cardiac surface marker SIRP&#945; and the fibroblast marker CD90 to create tissues containing a 3:1 ratio of these cell types, respectively, that are then mixed together and added to a collagen-based matrix solution. Resulting hECTs are, thus, completely defined in both their cellular and extracellular matrix composition.
Here we describe the construction of defined hECTs as a model system to understand mechanisms of cell-cell interactions in cell therapies, using an example of human bone marrow-derived mesenchymal stem cells (hMSC) that are currently being used in human clinical trials. The defined tissue composition is imperative to understand how the hMSCs may be interacting with the endogenous cardiac cell types to enhance tissue function. A bioreactor system is also described that simultaneously cultures six hECTs in parallel, permitting more efficient use of the cells after sorting.

This manuscript describes the creation of defined engineered cardiac tissues using surface marker expression and cell sorting. The defined tissues can then be used in a multi-tissue bioreactor to investigate mechanisms of cardiac cell therapy in order to provide a functional, yet controlled, model system of the human heart.

Human cardiac tissue engineering can fundamentally impact therapeutic discovery through the development of new species-specific screening systems that ...

Bioengineering

Generation and Expansion of Human Cardiomyocytes from Patient Peripheral Blood Mononuclear Cells

Generating patient-specific cardiomyocytes from a single blood draw has attracted tremendous interest in precision medicine on cardiovascular disease. Cardiac differentiation from human induced pluripotent stem cells (iPSCs) is modulated by defined signaling pathways that are essential for embryonic heart development. Numerous cardiac differentiation methods on 2-D and 3-D platforms have been developed with various efficiencies and cardiomyocyte yield. This has puzzled investigators outside the field as the variety of these methods can be difficult to follow. Here we present a comprehensive protocol that elaborates robust generation and expansion of patient-specific cardiomyocytes from peripheral blood mononuclear cells (PBMCs). We first describe a high-efficiency iPSC reprogramming protocol from a patient&#39;s blood sample using non-integration Sendai virus vectors. We then detail a small molecule-mediated monolayer differentiation method that can robustly produce beating cardiomyocytes from most human iPSC lines. In addition, a scalable cardiomyocyte expansion protocol is introduced using a small molecule (CHIR99021) that could rapidly expand patient-derived cardiomyocytes for industrial- and clinical-grade applications. At the end, detailed protocols for molecular identification and electrophysiological characterization of these iPSC-CMs are depicted. We expect this protocol to be pragmatic for beginners with limited knowledge on cardiovascular development and stem cell biology.

Here, we present a protocol to robustly generate and expand human cardiomyocytes from patient peripheral blood mononuclear cells.

Generating patient-specific cardiomyocytes from a single blood draw has attracted tremendous interest in precision medicine on cardiovascular disease. ...

Efficient Derivation of Human Cardiac Precursors and Cardiomyocytes from Pluripotent Human Embryonic Stem Cells with Small Molecule Induction

To date, the lack of a suitable human cardiac cell source has been the major setback in regenerating the human myocardium, either by cell-based transplantation or by cardiac tissue engineering1-3. Cardiomyocytes become terminally-differentiated soon after birth and lose their ability to proliferate. There is no evidence that stem/progenitor cells derived from other sources, such as the bone marrow or the cord blood, are able to give rise to the contractile heart muscle cells following transplantation into the heart1-3. The need to regenerate or repair the damaged heart muscle has not been met by adult stem cell therapy, either endogenous or via cell delivery1-3. The genetically stable human embryonic stem cells (hESCs) have unlimited expansion ability and unrestricted plasticity, proffering a pluripotent reservoir for in vitro derivation of large supplies of human somatic cells that are restricted to the lineage in need of repair and regeneration4,5. Due to the prevalence of cardiovascular disease worldwide and acute shortage of donor organs, there is intense interest in developing hESC-based therapies as an alternative approach. However, how to channel the wide differentiation potential of pluripotent hESCs efficiently and predictably to a desired phenotype has been a major challenge for both developmental study and clinical translation. Conventional approaches rely on multi-lineage inclination of pluripotent cells through spontaneous germ layer differentiation, resulting in inefficient and uncontrollable lineage-commitment that is often followed by phenotypic heterogeneity and instability, hence, a high risk of tumorigenicity6-8 (see a schematic in Fig. 1A). In addition, undefined foreign/animal biological supplements and/or feeders that have typically been used for the isolation, expansion, and differentiation of hESCs may make direct use of such cell-specialized grafts in patients problematic9-11. To overcome these obstacles, we have resolved the elements of a defined culture system necessary and sufficient for sustaining the epiblast pluripotence of hESCs, serving as a platform for de novo derivation of clinically-suitable hESCs and effectively directing such hESCs uniformly towards clinically-relevant lineages by small molecules12 (see a schematic in Fig. 1B). After screening a variety of small molecules and growth factors, we found that such defined conditions rendered nicotinamide (NAM) sufficient to induce the specification of cardiomesoderm direct from pluripotent hESCs that further progressed to cardioblasts that generated human beating cardiomyocytes with high efficiency (Fig. 2). We defined conditions for induction of cardioblasts direct from pluripotent hESCs without an intervening multi-lineage embryoid body stage, enabling well-controlled efficient derivation of a large supply of human cardiac cells across the spectrum of developmental stages for cell-based therapeutics.

We have established a protocol for induction of cardioblasts direct from pluripotent human embryonic stem cells maintained under defined conditions with small molecules, which enables derivation of a large supply of human cardiac progenitors and functional cardiomyocytes for cardiovascular repair.

To date, the lack of a suitable human cardiac cell source has been the major setback in regenerating the human myocardium, either by cell-based ...

Generation of Human Cardiomyocytes: A Differentiation Protocol from Feeder-free Human Induced Pluripotent Stem Cells

In order to investigate the events driving heart development and to determine the molecular mechanisms leading to myocardial diseases in humans, it is essential first to generate functional human cardiomyocytes (CMs). The use of these cells in drug discovery and toxicology studies would also be highly beneficial, allowing new pharmacological molecules for the treatment of cardiac disorders to be validated pre-clinically on cells of human origin. Of the possible sources of CMs, induced pluripotent stem (iPS) cells are among the most promising, as they can be derived directly from readily accessible patient tissue and possess an intrinsic capacity to give rise to all cell types of the body 1. Several methods have been proposed for differentiating iPS cells into CMs, ranging from the classical embryoid bodies (EBs) aggregation approach to chemically defined protocols 2,3. In this article we propose an EBs-based protocol and show how this method can be employed to efficiently generate functional CM-like cells from feeder-free iPS cells.

Pluripotent stem cells, either embryonic or induced pluripotent stem (iPS) cells, constitute a valuable source of human differentiated cells, including cardiomyocytes. Here, we will focus on cardiac induction of iPS cells, showing how to use them to obtain functional human cardiomyocytes through an embryoid bodies-based protocol.

In order to investigate the events driving heart development and to determine the molecular mechanisms leading to myocardial diseases in humans, it is ...

Generation of Ventricular-Like HiPSC-Derived Cardiomyocytes and High-Quality Cell Preparations for Calcium Handling Characterization

Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) provide a valuable human source for studying the basic science of calcium (Ca2+) handling and signaling pathways as well as high-throughput drug screening and toxicity assays. Herein, we provide a detailed description of the methodologies used to generate high-quality iPSC-CMs that can consistently reproduce molecular and functional characteristics across different cell lines. Additionally, a method is described to reliably assess their functional characterization through the evaluation of Ca2+ handling properties. Low oxygen (O2) conditions, lactate selection, and prolonged time in culture produce high-purity and high-quality ventricular-like cardiomyocytes. Similar to isolated adult rat cardiomyocytes (ARCMs), 3-month-old iPSC-CMs exhibit higher Ca2+ amplitude, faster rate of Ca2+ reuptake (decay-tau), and a positive lusitropic response to &#946;-adrenergic stimulation compared to day 30 iPSC-CMs. The strategy is technically simple, cost-effective, and reproducible. It provides a robust platform to model cardiac disease and for the large-scale drug screening to target Ca2+ handling proteins.

Here we describe and validate a method to consistently generate robust human induced pluripotent stem cell-derived cardiomyocytes and characterize their function. These techniques may help in developing mechanistic insight into signaling pathways, provide a platform for large-scale drug screening, and reliably model cardiac diseases.

Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) provide a valuable human source for studying the basic science of calcium (Ca2+) ...

In Vitro Differentiation of Human Mesenchymal Stem Cells into Functional Cardiomyocyte-like Cells

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